1. Field of the Invention
The invention is directed to a monitorable sealing arrangement for sealing a shaft relative to a stationary part, having a shaft sealing ring, a stator sealing ring, and a capacitive measuring arrangement, to a method for monitoring a sealing arrangement of this kind, and to a flow machine, particularly a gas compressor or gas expander with a sealing arrangement of this kind.
2. Description of the Related Art
In turbine flow engines or turbine flow machines, particularly gas compressors and gas expanders, one or more shafts that rotate during operation must be sealed relative to a stationary part such as a housing to seal off a high-pressure volume from a low-pressure volume. For this purpose, sliding seals are known in which a sealing gap is formed between a moving shaft sealing ring and a stator sealing ring. Work medium flows continuously through this sealing gap so that a thin gas film in the sealing gap seals off the high-pressure volume from the low-pressure volume.
For monitoring a sealing arrangement of this kind, U.S. Pat. No. 4,643,437 proposes arranging a thermal element in the stator ring to detect the width of the sealing gap.
For fluid seals in which a lubricating film is formed in the sealing gap, DE 197 23 327 A1 suggests, among others, a capacitive measuring arrangement in which a sensor in each of a shaft sealing ring and a stator sealing ring form a respective plate electrode of a plate capacitor. It is disadvantageous that this solution for fluid seals requires a measurement tap at the rotating shaft sealing ring.
DE 103 14 924 B1 proposes a gas seal or fluid seal having a depot for receiving leakage whose width is detected by a plate capacitor formed in a stator ring on both sides of the width to be detected. A sealing gap between a moving shaft sealing ring and a stator sealing ring is not provided.